If I recall, ULTRA played a non-trivial part in the Dunkirk landings by checking what the Nazis actually knew. Without that intelligence, it may not have succee

If I recall, ULTRA played a non-trivial part in the Dunkirk landings by checking what the Nazis actually knew. Without that intelligence, it may not have succeeded and things could indeed look very different today. Moving on from that, one of the people behind ULTRA went on to develop what we would recognise today as the cloud. In terms of cryptography, ULTRA was classified for decades after as the techniques developed were still in use.